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61.
The H-point standard addition method (HPSAM) was applied to the simultaneous determination of zinc(II) and cobalt(II). This method is based on the difference in the absorbance of methylthymol blue complexes of Zn(II) and Co(II) at pH 6 using different wavelength pairs. The results showed that Zn(II) and Co(II) can be determined simultaneously with concentration ratios of 20:1 and 1:7.5. Under working conditions, the proposed method was successfully applied to the simultaneous determination of zinc and cobalt in synthetic, drinking water and vitamin samples. 相似文献
62.
Fatemeh F. Bamoharram Majid M. Heravi Mina Roshani Ali Gharib Manouchehr Jahangir 《中国化学会会志》2007,54(4):1017-1020
Synthesis of aspirin at room temperature via O‐acetylation of salicylic acid in the presence of Preyssler type heteropolyacids has been investigated in order to contribute toward clean technology, which is the most important need of the society. All of the catalysts are recyclable and reusable. 相似文献
63.
The influence of group 15 various substituents and effect of metal centers on metal-borane interactions and structural isomers of transition metal-borane complexes W(CO)5(BH3 · AH3) and M(CO)5(BH3 · PH3) (A = N, P, As, and Sb; M = Cr, Mo, and W), were investigated by pure density functional theory at BP86 level. The following results were observed: (a) the ground state is monodentate, η1, with C1 point group; (b) in all complexes, the η1 isomer with CS symmetry on potential energy surface is the transition state for oscillating borane; (c) the η2 isomer is the transition state for the hydrogens interchange mechanism; (d) in W(CO)5(BH3 · AH3), the degree of pyramidalization at boron, interaction energy as well as charge transfer between metal and boron moieties, energy barrier for interchanging hydrogens, and diffuseness of A increase along the series A = Sb < As < P < N; (e) in M(CO)5(BH3 · PH3), interaction energy is ordered as M = W > Cr > Mo, while energy barrier for interchanging hydrogens decreases in the order of M = Cr > W > Mo. 相似文献
64.
《Fluid Phase Equilibria》2006,242(1):65-71
In this study, the individual ion activity coefficient in an aqueous solution is modeled with a new model. This model contains two physical significant ionic parameters regarding the ionic solvation and the closest distance of approach between ions in a solution. The present model was evaluated by the estimation of the individual activity coefficients of the ions of thirty electrolytes in aqueous solutions. The results showed that this model suitably predicts the individual ion activity coefficients in aqueous two-electrolyte solutions consisting of the binary pairs of electrolytes of NaCl, KCl, KBr and CaCl2 in a temperature range from 298.15 to 243.15 K. The results by this model were compared to the literature values. The average absolute relative deviations of vapor pressures showed acceptable agreement between experimental data and the results of this model. 相似文献
65.
K. Nazari A. Mahmoudi R. Khodafarin A. A. Moosavi-Movahedi A. Mohebi 《Journal of the Iranian Chemical Society》2005,2(3):232-237
The present research discusses the structure stabilizing and protecting effects of Ni2+ against suicide-peroxide inactivation of horseradish peroxidase (HRP). Suicide inactivation of HRP by hydrogen peroxide (3 mM) was monitored by measuring change in the absorbance of the colored product (tetraguaiacol) of the catalytic reaction cycle at 470 nm. Progress curves of the catalytic reaction cycle were obtained at 27 °C, phosphate buffer (5 mM), pH 7.0. The corresponding kinetic parameters (e.g., initial enzyme activity (αo) and the apparent rate constant (ki) of suicide inactivation of HRP by peroxide) were evaluated using a kinetic equation derived in this study. Comparative activatory and inhibitory effects of Ni2+ on the kinetics of suicide-peroxide inactivation of HRP are discussed. 相似文献
66.
《Tetrahedron: Asymmetry》2005,16(21):3584-3598
The synthesis and evaluation of four C2-symmetric nitroxides are presented. The nitroxides were evaluated for their ability to mediate the oxidation of several alcohols and found to have good catalytic activity. One enantioenriched nitroxide was found to kinetically resolve selected secondary alcohols with very modest selectivities. 相似文献
67.
Zohreh Habibi Peyman Salehi Maryam Yousefi Yahya Hejazi Ahmad Laleh Valiollah Mozaffarian Shiva Masoudi Abdolhossein Rustaiyan 《Chemistry of Natural Compounds》2006,42(6):689-692
The hydrodistilled oils from the aerial parts of Ferula latisecta and Mozaffariania insignis, which is endemic to Iran, were analyzed by GC and GC/MS. (Z)-Ocimenone (32.4%), (E)-ocimenone (20.3%), and cis-pinocarvone (11.4%) were the main components among the 22 constituents characterized in the oil of F. latisecta, representing 87.7% of the total components detected. Twenty-five compounds were identified in the oil of M. insignis, representing 99.0% of the total oil, with octyl acetate (41.1%), β-pinene (30.3%), and α-pinene (23.9%) as the main constituents. The essential oils were examined for their potential antimicrobial activities.
Published in Khimiya Prirodnykh Soedinenii, No. 6, pp. 561–563, November–December, 2006. 相似文献
68.
Ali MOGHIMI Mohammad SABER‐TEHRANI Syed WAQIF‐HUSAIN Majid MOHAMMADHOSSEINI 《中国化学》2007,25(12):1859-1865
A novel and selective method for the fast determination of trace amounts of chromium species in water samples has been developed. The procedure is based on the selective formation of chromium diethyldithiocarbamate complexes at different pH in the presence of Mn(II) as an enhancement agent of chromium signals followed by elution with organic eluents and determination by atomic flame absorption spectrometry. The maximum capacity of the employed disks was found to be (396±3) µg and (376±2) µg for Cr(III) and Cr(VI), respectively. The detection limit of the proposed method is 49 and 43 ng·L?1 for Cr(III) and Cr(VI), respectively. The proposed method was successfully applied for determination of chromium species Cr(III) and Cr(VI) in different water samples. 相似文献
69.
《Polyhedron》2005,24(16-17):2269-2273
Two ion-pair compounds, consisting of 1-(4′-R-benzyl)pyridinium ([RBzPy]+, R = NO2 (1) and Br (2)) and [Ni(dmit)2]− (dmit2− = 2-thioxo-1,3-dithion-4,5-dithiolato), have been synthesized and structurally characterized. The anions of [Ni(dmit)2]− stack into dimers, which further construct into two-leg ladder through terminal S⋯S interactions in 1, lateral S⋯S interactions in 2. The weak H-bonding interactions of C–H⋯S were observed in 2, while only weak van de Waals interactions between anion and cations in 1. The magnetic susceptibilities measured in 2–300 K indicate AFM exchange interaction domination both two compounds. A peculiar magnetic transition at ∼100 K was observed in 1. An AFM ordering below ∼11 K was found in 2, and the best fit to magnetic susceptibility above 45 K in this compound, using a dimer model with s = 1/2, give rise to Δ/kB = 36.1 K, zJ = −0.91 K, C = 3.2 × 10−3 emu K mol−1 and χ0 = −4.0 × 10−6 emu mol−1 with g of 2.0 fixed. 相似文献
70.
Keypour Hassan Khanmohammadi Hamid Wainwright Kevin P. Jameh-Bozorgi Saeed 《Transition Metal Chemistry》2004,29(5):523-527
The cyclocondensation of 2,6-diformylpyridine with N,N,N,N-tetrakis(2-aminoethyl)ethane-1,2-diamine (pentene) in the presence of MnII forms the [1 + 1] pendant arm Schiff-base macrocyclic complex, [MnL3]2+. The ligand is a 15-membered pentaaza macrocycle having two 2-aminoethyl pendant arms {L3= 6,9-bis(aminoethyl)-3,6,9,12,18-pentaazabicyclo[12.3.1]octadeca-1(18),2,12,14,16-pentene}. The complex, investigated by analytical, spectroscopic and magnetic techniques, supports the formation of a highly symmetrical pentagonal bipyramid complex with the MnII ion located within a pentaaza macrocycle and two pendant amines coordinating on opposite sides of a plane defined by the macrocycle and the metal ion. The structure of the complex was also verified by ab initio HF-MO calculations using a standard 3-21G basis set. 相似文献